1. Field of the Invention
The present invention relates to a portable timepiece in which, as in the case, for example, of a diver's watch for saturation diving, there is a possibility of the inner pressure of the timepiece exterior assembly being enhanced.
2. Background Information
There is known a diver's watch for saturation diving in which, to cope with the case in which the inner pressure of the timepiece exterior case has become higher than the outer pressure thereof, a button of an exhaust valve provided in this case is intentionally depressed, thereby forcibly discharging the gas inside the timepiece exterior case to the exterior of the case (See, for example, JP-A-5-172956 Patent Document 1).
The exhaust valve with which this diver's watch is equipped has a stepped hole formed in the case band of the timepiece exterior case, a button, a snap ring, a coil spring, and packing.
A small diameter hole portion of the stepped hole is open to the inner side of the case band, and a large diameter hole portion of the stepped hole is open to the exterior of the case band. The button has an operating portion fit-engaged with the large diameter hole portion, and a shaft portion passed through the small diameter hole portion. The snap ring, which prevents detachment of the button from the stepped hole, is connected to the shaft portion inside the timepiece exterior case. The coil spring is accommodated in the large diameter hole portion while wound around the shaft portion, urging the button toward the outer side of the case band. The packing is fixed to the shaft portion. In the normal state, in which the button is not being depressed, this packing exhibits interference while in contact with the inner surface of a pipe attached to the small diameter hole portion or this hole portion; in the state in which the button has been pushed in, it is arranged inside the case band so as not to exhibit any interference.
Thus, simultaneously with the pushing-in of the button, the packing is removed from the small diameter hole portion of the stepped hole; as communication is established between the interior and the exterior of the case band via the stepped hole, it is possible to discharge the gas inside the timepiece exterior case to the exterior of the case via the stepped hole.
The packing of the diver's watch of Patent Document 1 is not compressed by the pressure of the outside air striving to enter the interior from the exterior of the timepiece exterior case, so that, in saturation diving, the airtightness performance of the packing is not enhanced. Thus, the possibility of helium gas used in saturation diving being transmitted through the packing to enter the timepiece exterior case is high; thus, the inner pressure of the case is likely to increase.
Further, in a situation in which the exhaust valve is operated after saturation diving, there is a possibility of water being accumulated in the large diameter hole portion of the stepped hole, and some water adhering to the wet hand of the diver may be allowed to enter the large diameter hole portion. Further, in the case of exhaust valve pushing-in operation under rainy weather, rain water may be allowed to enter the large diameter hole portion. If the exhaust operation is performed in such a situation, there may be a fear of the water in the large diameter hole portion being allowed to enter the timepiece exterior case immediately after the completion of the exhaust, with the packing exhibiting no interference.
As described above, in the prior art technique, gas is likely to be transmitted inside the timepiece exterior case via the exhaust valve from the outside; further, there is a fear of water being allowed to enter from the outside as the degassing operation is completed.